On Tuesday, TWRA issued a release saying biologists are still uncertain as what caused the kill.

Fisheries Biologist Jim Negus believes that the fish kill was relatively short-lived and occurred between late Thursday and Saturday morning in the area below Alcoa Highway and the mouth of the river where it enters the Tennessee.

"Oftentimes, fish kills are caused by low dissolved oxygen content however, there is too much flow in this area of both the Tennessee and Little Rivers," Negus stated. The biologist also noted that witnesses did not notice any fish struggling as would be the case in a low dissolved oxygen event, the fish just showed up dead.

Negus interviewed several people who saw the dead fish, and talked to the manager of a sewage treatment plant that is upstream from the kill area. The manager told Negus that nothing unusual had occurred at the facility this week.

TWRA said The Tennessee Department of Environment and Conservation has also investigated the event and has not identified any industrial sources for possible contaminants.

Negus estimates that between 2,000-4,000 fish were killed and as many as 15 species were affected.